The present disclosure relates to an optical amplifier and an optical amplifying method.
In the optical engineering field, as a device that amplifies intensity of a laser beam, a semiconductor optical amplifier (SOA) has attracted attention. The SOA is a device having a structure similar to that of a laser diode (LD) and causes stimulated emission in a semiconductor layer with a laser beam incident on the semiconductor layer that is made in an inverted distribution state by supplying predetermined current, and amplifies the intensity of the laser beam.
In recent years, SOAs having a variety of structures have been developed so as to increase performance thereof. For example, Jan C. Balzer et al., Photonics West 2012, USA, Paper 8277-39, disclose an SOA that amplifies a pulse-oscillated laser beam (pulsed laser beam), in which electrodes for supplying current are divided into two parts and current having different values is supplied to the respective two parts of the electrodes, so that pulse frequency of the pulsed laser beam is adjusted in a region corresponding to a former-stage electrode and the intensity of the pulsed laser beam is amplified in a region corresponding to a latter-stage electrode.
Meanwhile, in the optical recording field using a laser beam, a laser beam with a relatively high output, for example, having peak power of about 100 W, is required. Accordingly, for a laser beam having a blue wavelength band of about 405 (nm) for example, an SOA aiming to output such a laser beam with a relatively high output more stably has been developed. For example, JP 2012-248745A discloses a light source apparatus having an SOA, which adjusts a cross-sectional area of a waveguide of the SOA and changes the magnification of a laser beam (incident light) that is incident on a former stage of the SOA, thereby making only one peak appear in the laser beam that is finally output and suppressing variations in the peak position.